Solar Tadpole-Like Jets Seen With NASA’S IRIS Add New Clue to Age-Old Mystery

Images from IRIS show the tadpole-shaped jets containing pseudo-shocks streaking out from the Sun

Credits: Abhishek Srivastava IIT (BHU)/Joy Ng, NASA’s Goddard Space Flight Center

For 150 years scientists have been trying to figure out why the wispy upper atmosphere of the Sun — the corona — is over 200 times hotter than the solar surface. This region, which extends millions of miles, somehow becomes superheated and continually releases highly charged particles, which race across the solar system at supersonic speeds.

When those particles encounter Earth, they have the potential to harm satellites and astronauts, disrupt telecommunications, and even interfere with power grids during particularly strong events. Understanding how the corona gets so hot can ultimately help us understand the fundamental physics behind what drives these disruptions.

In recent years, scientists have largely debated two possible explanations for coronal heating: nanoflares and electromagnetic waves. The nanoflare theory proposes bomb-like explosions, which release energy into the solar atmosphere. Siblings to the larger solar flares, they are expected to occur when magnetic field lines explosively reconnect, releasing a surge of hot, charged particles. An alternative theory suggests a type of electromagnetic wave called Alfvén waves might push charged particles into the atmosphere like an ocean wave pushing a surfer. Scientists now think the corona may be heated by a combination of phenomenon like these, instead of a single one alone. 

The new discovery of pseudo-shocks adds another player to that debate. Particularly, it may contribute heat to the corona during specific times, namely when the Sun is active, such as during solar maximums — the most active part of the Sun’s 11-year cycle marked by an increase in sunspots, solar flares and coronal mass ejections.

The discovery of the solar tadpoles was somewhat fortuitous. When recently analyzing data from NASA’s Interface Region Imaging Spectrograph, or IRIS, scientists noticed unique elongated jets emerging from sunspots ­— cool, magnetically-active regions on the Sun’s surface — and rising 3,000 miles up into the inner corona. The jets, with bulky heads and rarefied tails, looked to the scientists like tadpoles swimming up through the Sun’s layers.

“We were looking for waves and plasma ejecta, but instead, we noticed these dynamical pseudo-shocks, like disconnected plasma jets, that are not like real shocks but highly energetic to fulfill Sun's radiative losses,” said Abhishek Srivastava, scientist at the Indian Institute of Technology (BHU) in Varanasi, India, and lead author on the new paper in Nature Astronomy.

Using computer simulations matching the events, they determined these pseudo-shocks could carry enough energy and plasma to heat the inner corona.

A computer simulation shows how the pseudo-shock is ejected and becomes disconnected from the plasma below (green)

Credits: Abhishek Srivastava IIT (BHU)/Joy Ng, NASA’s Goddard Space Flight Center

The scientists believe the pseudo-shocks are ejected by magnetic reconnection — an explosive tangling of magnetic field lines, which often occurs in and around sunspots. The pseudo-shocks have only been observed around the rims of sunspots so far, but scientists expect they’ll be found in other highly magnetized regions as well.

The tadpole-shaped pseudo-shocks, shown in dashed white box, are ejected from highly magnetized regions on the solar surface. Credits: Abhishek Srivastava IIT (BHU)/Joy Ng, NASA’s Goddard Space Flight Center

Over the past five years, IRIS has kept an eye on the Sun in its 10,000-plus orbits around Earth. It’s one of several in NASA’s Sun-staring fleet that have continually observed the Sun over the past two decades. Together, they are working to resolve the debate over coronal heating and solve other mysteries the Sun keeps.

“From the beginning, the IRIS science investigation has focused on combining high-resolution observations of the solar atmosphere with numerical simulations that capture essential physical processes,” said Bart De Pontieu research scientist at Lockheed Martin Solar & Astrophysics Laboratory in Palo Alto, California. “This paper is a nice illustration of how such a coordinated approach can lead to new physical insights into what drives the dynamics of the solar atmosphere.”

The newest member in NASA’s heliophysics fleet, Parker Solar Probe, may be able to provide some additional clues to the coronal heating mystery. Launched in 2018, the spacecraft flies through the solar corona to trace how energy and heat move through the region and to explore what accelerates the solar wind as well as solar energetic particles. Looking at phenomena far above the region where pseudo-shocks are found, Parker Solar Probe’s investigation hopes to shed light on other heating mechanisms, like nanoflares and electromagnetic waves. This work will complement the research conducted with IRIS.

“This new heating mechanism could be compared to the investigations that Parker Solar Probe will be doing,” said Aleida Higginson, deputy project scientist for Parker Solar Probe at Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland. “Together they could provide a comprehensive picture of coronal heating.”

Related Links:

• Learn more about NASA’s IRIS Mission
• NASA’s Parker Solar Probe and the Curious Case of the Hot Corona
• Learn more about NASA's Parker Solar Probe

By Mara Johnson-Groh
NASA’s Goddard Space Flight Center, Greenbelt, Md.

Editor: Rob Garner

Source: NASA/IRIS

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NASA's IRIS Spots Its Largest Solar Flare

On Jan. 28, 2014, NASA's newly-launched Interface Region Imaging Spectrometer, or IRIS, observed its strongest solar flare to date.Image Credit: NASA/IRIS/SDO/Goddard Space Flight Center.  Download high resolution video

On Jan. 28, 2014, NASA's IRIS witnessed its strongest solar flare since it launched in the summer of 2013. Image Credit: NASA/IRI. Large Image

On Jan. 28, 2014, NASA's Interface Region Imaging Spectrograph, or IRIS, witnessed its strongest solar flare since it launched in the summer of 2013. Solar flares are bursts of x-rays and light that stream out into space, but scientists don't yet know the fine details of what sets them off.

IRIS peers into a layer of the sun's lower atmosphere just above the surface, called the chromosphere, with unprecedented resolution. However, IRIS can't look at the entire sun at the same time, so the team must always make decisions about what region might provide useful observations. On Jan. 28, scientists spotted a magnetically active region on the sun and focused IRIS on it to see how the solar material behaved under intense magnetic forces. At 2:40 p.m. EST, a moderate flare, labeled an M-class flare -- which is the second strongest class flare after X-class – erupted from the area, sending light and x-rays into space.

IRIS studies the layer of the sun’s atmosphere called the chromosphere that is key to regulating the flow of energy and material as they travel from the sun's surface out into space. Along the way, the energy heats up the upper atmosphere, the corona, and sometimes powers solar events such as this flare.

IRIS is equipped with an instrument called a spectrograph that can separate out the light it sees into its individual wavelengths, which in turn correlates to material at different temperatures, velocities and densities. The spectrograph on IRIS was pointed right into the heart of this flare when it reached its peak, and so the data obtained can help determine how different temperatures of material flow, giving scientists more insight into how flares work.

The IRIS mission is managed by the Lockheed Martin Solar and Astrophysics Laboratory of the ATC in Palo Alto, Calif. NASA’s Ames Research Center in Moffett Field, Calif., is responsible for mission operations and the ground data system. The Ames Pleiades supercomputer is used to carry out many of the numerical simulations that are led by the University of Oslo. The IRIS telescope was designed and built by the Smithsonian Astrophysical Observatory while Montana State University faculty and students assisted in the design of the spectrograph. A large volume of science data is downlinked via Kongsberg Satellite Services, (KSAT) facilities through a cooperative agreement between NASA and the Norwegian Space Centre.  NASA’s Goddard Space Flight Center in Greenbelt, Md., oversees the Explorers Program from which IRIS evolved.

Karen C. Fox
NASA's Goddard Space Flight Center, Greenbelt, Md.

NASA IRIS: Improving Our View Of the Sun

This image from the Japan Aerospace Exploration Agency’s Hinode mission shows the lower regions of the sun’s atmosphere, the interface region, which a new mission called the Interface Region Imaging Spectrograph, or IRIS, will study in exquisite detail. Where previous missions have been able to image material at only a few predetermined temperatures in this region, IRIS will observe a wide range of temperatures from 5,000 kelvins to 65,000 kelvins (8,540 F to 116,540 F), and up to 10 million kelvins (about 18 million F) during solar flares. Its images will resolve structures down to 150 miles across. Credit: JAXA/Hinod.   › View larger

In late June 2013, NASA will launch a new set of eyes to offer the most detailed look ever of the sun’s lower atmosphere, called the interface region. This region is believed to play a crucial role in powering the sun’s dynamic million-degree atmosphere, the corona. The Interface Region Imaging Spectrograph or IRIS mission will provide the best resolution so far of the widest range of temperatures for of the interface region, an area that has historically been difficult to study.

"This region is crucial for understanding how the corona gets so hot,” said Joe Davila, IRIS project scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. "For the first time, we will have the capability to observe it at fundamental physical scale sizes and see details that have previously been hidden."

IRIS’s capabilities are uniquely tailored to unravel the interface region by providing both high-resolution images and a kind of data known as spectra.

For its high-resolution images, IRIS will capture data on about one percent of the sun at a time. While these are relatively small snapshots, IRIS will be able to see very fine features, as small as 150 miles across.

“We have some great space observatories currently looking at the sun,” said Bart DePontieu, the IRIS science lead at Lockheed Martin in Palo Alto, Calif. “But when it comes to the interface region, we’ve never been able to resolve individual structures. We have been able only to see conglomerates of various structures. Now we will finally be able to observe the details.”

IRIS’s images will be three to four times as detailed as the images from NASA’s Solar Dynamics Observatory – though SDO can observe the whole sun at once. SDO’s wavelengths are not tailored, however, to see the interface region. Scientists can use IRIS observations to hone in on smaller details while working with the larger instruments, such as SDO or the Japan Aerospace Exploration Agency’s Hinode, to capture images of the entire sun. Together, the observatories will explore how the corona works and impacts Earth – SDO and Hinode monitoring the solar surface and outer atmosphere, with IRIS watching the region in between.

These movies use data from the Japan Aerospace Exploration Agency’s Hinode mission to provide an example of IRIS’ improved resolution over previous observations. Credit: JAXA/Hinode/De Pontieu.  › Download video 

Ultraviolet images look at only one wavelength of light at a time, but IRIS will also provide spectra, a kind of data that can show information about many wavelengths of light at once. Spectrographs split the sun’s light into its various wavelengths and measure how much of any given wavelength is present. This is then portrayed on a graph showing spectral "lines" – taller lines correspond to wavelengths in which the sun emits relatively more radiation.

Each spectral line also corresponds to a given temperature, so this provides information about how much material of a particular temperature is present. The images from IRIS' telescope will record observations of material at specific temperatures, ranging from 5,000 kelvins to 65,000 kelvins (8,540 F to 116,540 F) -- and up to 10 million kelvins (about 18 million F) during solar flares -- a range best suited to observe material on the sun's surface and in the interface region.

“By looking at spectra of material in these temperature ranges, we can also diagnose velocity and perhaps density of the material, too,” said De Pontieu.

The IRIS instrument will capture a new image every five to 10 seconds, and spectra about once every two seconds. These unique capabilities will be coupled with state-of-the-art 3-D numerical modeling sophisticated enough to deal with the complexity of this region. The modeling makes use of supercomputers at NASA’s Ames Research Center, Moffet Field, Calif.

In combination, IRIS’ resolution, fast imaging rate, wide temperature coverage and computer modeling will enable scientists for the first time to track solar material as it is accelerated and heated in the interface region and thus help pinpoint where and how the plasma gains energy and heat along its travels through the lower levels of the solar atmosphere.

IRIS was developed by Lockheed Martin as a NASA Small Explorer mission. The NASA Explorer Program is designed to provide frequent, low-cost access to space for heliophysics and astrophysics missions using small- to mid-sized spacecraft. Goddard manages the Explorer Program for the agency’s Science Mission Directorate in Washington. Major contributions for IRIS were provided by Lockheed Martin Sensing and Exploration Systems, NASA’s Ames Research Center, Smithsonian Astrophysical Observatory, Montana State University, Stanford University, the Norwegian Space Centre and the University of Oslo.

For more information about NASA's IRIS mission, please visit: http://www.nasa.gov/iris

 

Karen C. Fox
NASA's Goddard Space Flight Center, Greenbelt, Md.